The present invention relates to the field of vapor recovery and more particularly involves the recovery of volatile organic compounds (VOCs) during the loading and/or unloading of shipping vehicles, such as trucks, railroad cars, airplanes, and marine vehicles, when such vehicles are being loaded with liquids such as fuels, including gasoline and distillates. The present invention utilizes a vacuum-assisted system controlled by a programmable logic controller to remove and safely handle volatile vapors during the loading and unloading of vehicles.
During the loading of materials such as gasolines and middle distillates, VOCs are displaced and generated, which in most instances generally escape into the atmosphere and contribute to the overall air pollution burden of the geographic area. While governments have mandated air quality standards and attempted to remove such contaminants from the air, one of the pollution sources remains the transfer of liquids such as gasolines and other distillates in loading terminals and in other areas. It has been very difficult to transfer such liquids without the loss of vapors during the transfer process, which loss results in addition of the hydrocarbon material into the ambient air. While the prior art contains many attempts to collect such vapors and prevent their loss into the atmosphere, these efforts have not been entirely successful for several reasons.
One such reason involves the inherent desire of the vehicle operator for rapid loading. In many instances it was found that elaborate recovery systems were being disabled by the vehicle operators in order to speed up the loading operation. The vapor recovery systems were easily bypassed and therefore were ineffective.
Another disadvantage in conventional loading system vacuum recovery units is that they tended to be leaky and were not successful in entrapping all of the escaping vapors. Also, many conventional systems for vapor recovery were found to be extremely dangerous because they created explosive mixtures of vapors and air which were then very difficult to handle.
The present invention overcomes these deficiencies by providing a logic-controlled system having sufficient interlocks to prevent bypassing of the system and sufficient safety features to prevent occurrence to vessel collapse, of dangerous mixtures, or leaking conditions.